View
2
Download
0
Category
Preview:
Citation preview
SYNTHESIS OF BUCKYPAPER SUPPORTED
IONIC LIQUID MEMBRANE FOR
PERVAPORATION PROCESS
ONG YIT THAI
UNIVERSITI SAINS MALAYSIA
2016
SYNTHESIS OF BUCKYPAPER SUPPORTED IONIC LIQUID MEMBRANE
FOR PERVAPORATION PROCESS
by
ONG YIT THAI
Thesis submitted in fulfillment of the
requirements for the degree of
Doctor of Philosophy
February 2016
ii
ACKNOWLEDGEMENT
First of all, I would like to express my deepest and most heart-felt gratitude
to my beloved parents and siblings for their endless love and encouragement
throughout my studies.
I would like to give my sincere thanks to my dedicated supervisors Assoc.
Prof. Dr. Tan Soon Huat for his supervision and enormous effort spent in guiding and
helping me throughout my studies. My accomplishment of this research project is a
direct reflection of high quality supervision work from my supervisors.
Next, I would like to express my gratitude to all the administrative staffs and
laboratory technicians of School of Chemical Engineering, Universiti Sains Malaysia
for giving me full support throughout my research work.
I would to like to show my token of appreciation to all my beloved friends
and colleagues: Thiam Leng, Hui Sun, Man Kee, Kian Fei, Henry, Jing Yao, Mei Kee
and Yee Jie for their unparalleled help, kindness and moral support towards me. Not
forgotten are my juniors, Qian Wen and others for their sincere support given to me. I
might not able to achieve what I want to be without the support from all of my
friends and colleagues.
iii
Last but not least, I would like to acknowledge the financial supports from
MyPhd fellowship from the Ministry of Higher Education of Malaysia, Universiti
Sains Malaysia Research University (RU) grant (A/C:814142), the Postgraduate
Research Grant Scheme (PRGS) (A/C:8045034), and USM Membrane Cluster Grant
(A/C:81610013).
Thank you very much!
Ong Yit Thai, 2016
iv
TABLE OF CONTENTS
Acknowledgement.………………………………………………………….... ii
Table of Contents.…………………………………………………………….. iv
List of Tables.……………………………………………………………….... viii
List of Figures.………………………………………………………………... xi
List of Abbreviations.……………………………………………………….... xv
List of Symbols.………………………………………………………………. xvii
Abstrak.……………………………………………………………………….. xix
Abstract.………………………………………………………………………. xxi
CHAPTER 1 - INTRODUCTION
1.1 Pervaporation.………………………………………………………….. 1
1.2 Requirement for pervaporation membrane…………………………….. 3
1.2.1 Polymeric membrane…………………………………………. 6
1.2.2 Inorganic membrane………………………………………….. 7
1.2.3 Mixed-matrix membrane……………………………………... 8
1.3 Liquid membrane………………………………………………………. 9
1.4 Problem Statement……………………………………………………... 11
1.5 Objectives……………………………………………………………… 14
1.6 Scope of the study……………………………………………………... 14
1.7 Organization of the thesis……………………………………………… 16
CHAPTER 2 - LITERATURE REVIEW
2.1 Supported liquid membrane…………………………………………… 18
2.1.1 Liquid membrane……………………………………………... 21
2.1.2 Supporting membrane………………………………………… 24
2.2 Stability of supported liquid membrane……………………………….. 27
2.3 Pervaporation studies using supported liquid membrane……………… 29
2.4 Buckypaper…………………………………………………………….. 39
2.5 Pervaporation case studies……………………………………………... 45
2.5.1 Pervaporation dehydration of ethylene glycol/water binary
mixture………………………………………………………... 45
v
2.5.2 Pervaporation dehydration of ethyl acetate/ethanol/water
ternary azeotropic mixture……………………………………. 52
2.6 Evaluation of the separation performance in pervaporation process…... 56
2.7 Fundamental and mathematical modeling of pervaporation…………... 60
CHAPTER 3 - MATERIALS AND METHODOLOGY
3.1 Raw materials and chemicals………………………………………….. 66
3.1.1 Raw materials…………………………………………………. 66
3.1.2 Chemicals……………………………………………………... 66
3.2 Multi-walled carbon nanotubes treatment……………………………... 68
3.3 Preparation of polyvinyl alcohol and ionic liquid mixture…………….. 68
3.4 Preparation of buckypaper and buckypaper supported ionic liquid
membrane……………………………………………………………… 69
3.4.1 Preparation of buckypaper supported ionic liquid membrane
with different surface density of buckypaper…………………. 70
3.4.2 Preparation of buckypaper supported ionic liquid membrane
with different concentration of [Bmim][BF4]-PVA…………... 70
3.5 Liquid sorption study…………………………………………………... 71
3.6 Characterization………………………………………………………... 72
3.6.1 Thermogravimetric analysis…………………………………... 72
3.6.2 Scanning electron microscopy equipped with energy
dispersive X-ray………………………………………………. 72
3.6.3 Ultraviolet visible spectroscopy………………………………. 73
3.6.4 Contact angle measurement…………………………………... 73
3.6.5 Mechanical properties study………………………………….. 73
3.7 Pervaporation…………………………………………………………... 74
3.7.1 Pervaporation test rig…………………………………………. 74
3.7.2 Experimental operation……………………………………….. 77
3.7.3 Process studies………………………………………………... 77
3.7.4 Permeate sample analysis…………………………………….. 81
3.7.5 Mathematical modeling of the pervaporation process………... 82
3.7.6 Calculation of the activity coefficient………………………… 84
vi
CHAPTER 4 - RESULTS AND DISCUSSION
4.1 Thermogravimetric analysis…………………………………………… 88
4.2 Ultraviolet visible spectroscopy……………………………………….. 91
4.3 Scanning electron microscopy equipped with energy dispersive X-
ray……………………………………………………………………… 94
4.4 Effect of buckypaper surface density on the immobilization of
[Bmim][BF4]-PVA…………………………………………………….. 96
4.5 Effect of buckypaper surface density on mechanical properties of
buckypaper supported ionic liquid membrane………………………… 98
4.6 Contact angle measurement……………………………………………. 100
4.7 Liquid sorption study…………………………………………………... 102
4.7.1 Ethylene glycol and water…………………………………….. 102
4.7.2 Ethyl acetate, ethanol and water……………………………… 105
4.8 Pervaporation dehydration of ethylene glycol/water binary mixture….. 108
4.8.1 Effect of [Bmim][BF4] content in the buckypaper supported
ionic liquid membrane………………………………………... 108
4.8.2 Effect of feed concentration…………………………………... 111
4.8.3 Effect of feed temperature……………………………………. 115
4.8.4 Effect of downstream pressure………………………………... 120
4.8.5 Membrane stability in pervaporation dehydration of ethylene
glycol/water binary mixture…………………………………... 126
4.8.6 Comparison of the present pervaporation performance with
literature reported data………………………………………... 128
4.9 Pervaporation dehydration of ethyl acetate/ethanol/water ternary
mixture…………………………………………………………………. 130
4.9.1 Pervaporation separation of ethyl acetate/water binary
mixture………………………………………………………... 130
4.9.2 Pervaporation separation of ethanol/water binary mixture…… 134
4.9.3 Pervaporation separation of ethyl acetate/ethanol binary
mixture………………………………………………………... 137
4.9.4 Pervaporation dehydration of ethyl acetate/ ethanol/ water
ternary azeotropic mixture……………………………………. 141
4.9.5 Effect of feed temperature……………………………………. 144
vii
4.9.6 Effect of downstream pressure………………………………... 149
4.9.7 Membrane stability in pervaporation dehydration of ethyl
acetate/ ethanol/water ternary azeotropic mixtures…………… 152
4.9.8 Comparison of the present pervaporation performance with
literature reported data………………………………………... 153
4.10 Mathematical modeling on the pervaporation dehydration of ethylene
glycol/water binary mixture…………………………………………… 155
4.10.1 Estimation on the sorption behavior of the membrane……….. 155
4.10.2 Estimation on the pervaporation performance as a function of
feed concentration…………………………………………….. 159
4.10.3 Estimation on the pervaporation performance as a function of
feed temperature………………………………………………. 168
4.10.4 Estimation on the pervaporation performance as a function of
downstream pressure………………………………………….. 178
CHAPTER 5 - CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions……………………………………………………………. 187
5.2 Recommendations……………………………………………………... 190
REFERENCES………………………………………………………………... 191
APPENDICES
Appendix A Calculation of binary interaction parameter
Appendix B Calculation of buckypaper surface density
Appendix C SEM images for 5.88mg/cm2 buckypaper
Appendix D Calculation of pervaporation performances
Appendix E Algorithm for parameter estimation using modified
Maxwell-Stefan equation
Appendix F Determine the variables using Solver function in Microsoft
Excel.
LIST OF PUBLICATIONS
viii
LIST OF TABLES
Page
Table 1.1 Summary of the membranes for pervaporation 5 Table 1.2 Charaterization techniques used in this research work 15 Table 2.1 Physical properties of the commonly used liquid
membranes 24
Table 2.2 Pervaporation studies using SLMs and SILMs 37 Table 2.3 Physical properties of ethylene glycol and water 46 Table 2.4 Summary of the pervaporation performances of various
membranes in dehydration of ethylene glycol 51
Table 2.5 Summary of the pervaporation performances of various
membranes in dehydration of ethyl acetate/ethanol/water azeotropic mixtures
55
Table 3.1 List of chemicals used in experimental work 67 Table 3.2 Experimental studies on the effect of feed concentration of
water for dehydration of ethylene glycol 78
Table 3.3 Experimental studies on the effect of feed temperature for
dehydration of ethylene glycol 78
Table 3.4 Experimental studies on the effect of downstream pressure
for dehydration of ethylene glycol 79
Table 3.5 Experimental runs for the pervaporation studies of ethyl
acetate/ethanol/ water 80
Table 3.6 Volume parameter and surface parameter 85 Table 3.7 Interaction parameters of groups 86 Table 4.1 Effect of BP surface density on the immobilization of
[Bmim][BF4]-PVA 96
Table 4.2 Effect of BP surface density on the mechanical properties
of the BP-SILM. 99
Table 4.3 Contact angle measurements as a function of weight
fraction of [Bmim][BF4] in BP-SILM 101
ix
Table 4.4 Sorption data of BP-SILMs as a function of content of [Bmim][BF4] in BP-SILM
103
Table 4.5 Activation energy, EJi and EPi values for water and
ethylene glycol 118
Table 4.6 Driving force generated for water and ethylene glycol at
various feed temperature and downstream pressure at feed water concentration of 10 wt.%
122
Table 4.7 Comparison with the literature reported data on the
pervaporation dehydration of ethylene glycol/water mixture
129
Table 4.8 Performance of BP-SILM-70 for the pervaporation
dehydration of ternary azeotropic mixture of ethyl acetate/ethanol/water at 30°C and 5 mmHg
143
Table 4.9 Activation energy, Eji and EPi for ethyl acetate, ethanol and
water 147
Table 4.10 Comparison with the literature reported data on the
pervaporation dehydration of ethyl acetate/ethanol/water ternary azeotropic mixture
154
Table 4.11 Results data on the activity of water and ethylene glycol at
various concentration solution mixtures 156
Table 4.12 Estimated adjustable parameters, 𝑠1, 𝑠2 and m for water 156 Table 4.13 Solubility coefficient for water at various concentrations of
solution mixtures and the predicted sorption of BP-SILM-70
157
Table 4.14 Predicted sorption concentration of water and ethylene
glycol in various feed concentration. 159
Table 4.15 Diffusion coefficient of water and ethylene glycol and the
coupled diffusion coefficient at various feed concentration 161
Table 4.16 R2 value for the pervaporation performances of the BP-
SILM-70 predicted with modified Maxwell-Stefan equation
167
Table 4.17 Activity, solubility coefficient and sorption concentration
of water and ethylene glycol as a function of feed temperature
168
x
Table 4.18 The activation energy of diffusion, 𝐸𝐷 and enthalpy heat of sorption, ΔHS for water and ethylene glycol
171
Table 4.19 Diffusion coefficient for water and ethylene glycol at
various feed temperature 171
Table 4.20 R2 value for the pervaporation performances of the BP-
SILM-70 predicted with modified Maxwell-Stefan equation
178
Table 4.21 Diffusion coefficient for water and ethylene glycol at
various downstream pressures 181
Table 4.22 R2 value for the pervaporation performances of the BP-
SILM-70 predicted with modified Maxwell-Stefan equation
186
xi
LIST OF FIGURES
Page Figure 1.1 Overview of pervaporation process 2 Figure 1.2 Schematic diagram of a MMM 8 Figure 1.3 Configuration of liquid membrane. (a) BLM, (b) ELM and (c)
SLM. F is the feed phase, M is the membrane phase, and R is the receiving phase
10
Figure 1.4 Schematic diagram of the BP-SILM 13 Figure 2.1 (a) Schematic diagram of the SLM without coating. (b)
Schematic diagram of the SLM with a plasma-polymerized ultrathin silicone coating
31
Figure 2.2 Flux and permeability data obtained with 2.5 µm thick pure
silicone rubber membrane and 10 µm zeolite-silicone rubber mixed-matrix membrane
58
Figure 2.3 The pervaporation data sets of the separation of toluene from
toluene/methanol mixtures using crosslink natural rubber in term of (a) permeation flux and separation factor, (b) permeance and selectivity
59
Figure 3.1 Schematic diagram of permeation cell (the drawing is not to
scale) 75
Figure 3.2 Process flow diagram of the pervaporation test rig 76 Figure 3.3 Schematic diagram of the research methodology 87 Figure 4.1 (a) Weight loss, and (b) Derivative weight of raw MWCNTs
and oxidized MWCNTs 89
Figure 4.2 (a) Weight loss and (b) Derivative weight plots of pure PVA,
[Bmim][BF4]-PVA in 30/70, 50/50 and 70/30 wt.%, and pure [Bmim][BF4]
90
Figure 4.3 (a) UV-visible absorption spectrum of MWCNTs dispersion in
ethanol with different sonication time. (b) Absorbance at 908 nm against sonication time
93
Figure 4.4 SEM images of surface morphology of (a) 5.31 mg/cm2 BP, (b)
BP-SILM with 5.31 mg/cm2 BP, (c) PVDF membrane filter and the cross sectional view of (d) BP and (e) BP-SILM
95
xii
Figure 4.5 Stress vs strain curves for BP-SILM with different BP surface
density 98
Figure 4.6 Chemical structure of [Bmim]+ cation and [BF4]- anion in
[Bmim][BF4] 103
Figure 4.7 Degree swelling of BP-SILM-70 at various water
concentrations in ethylene glycol and water binary mixture 104
Figure 4.8 Degree of swelling of BP-SILM-70 at various feed solution
conditions 106
Figure 4.9 Effect of different type of membrane on the (a) permeation
flux, (b) permeate concentration and separation factor and (c) permeance and selectivity in pervaporation dehydration of ethylene glycol/water with 10 wt.% water in the feed solution at 30°C and a downstream pressure of 5 mmHg
109
Figure 4.10 Effect of feed concentration of water on the (a) permeation flux, (b) permeate concentration and separation factor and (c) permeance and selectivity in pervaporation dehydration of ethylene glycol/water at 30 °C and a downstream pressure of 5 mmHg
112
Figure 4.11 Effect of feed temperature on the (a) permeation flux, (b) permeate concentration and separation factor and (c) permeance and selectivity in pervaporation dehydration of ethylene glycol/water with 10 wt.% water in the feed solution and a downstream pressure of 5 mmHg
116
Figure 4.12 Arrhenius plot of semi-logarithmic of (a) permeation flux and (b) permeance against the reciprocal of absolute temperature
119
Figure 4.13 Effect of downstream pressure on the (a) permeation flux, (b)
permeate concentration and separation factor and (c) permeance and selectivity in pervaporation dehydration of ethylene glycol/water with 10 wt.% water in the feed solution at 30°C
124
Figure 4.14 Pervaporation performances of BP-SILM-70 in dehydration of ethylene glycol/water for 120 hours operation time with 10 wt.% water in the feed solution at 30°C and a downstream pressure of 5 mmHg
128
xiii
Figure 4.15 Effect of the feed concentration of water on the (a) permeation
flux, (b) permeate concentration and separation factor and (c) permeance and selectivity in the pervaporation separation of ethyl acetate/water at 30°C and a downstream pressure of 5 mmHg
131
Figure 4.16 Effect of feed concentration of water on the (a) permeation flux, (b) permeate concentration and separation factor and (c) permeance and selectivity in the pervaporation separation of ethanol/water at 30°C and a downstream pressure of 5 mmHg
135
Figure 4.17 Effect of feed concentration of ethanol on the (a) permeation
flux, (b) permeate concentration and separation factor and (c) permeance and selectivity in the pervaporation separation of ethyl acetate/ethanol at 30°C and a downstream pressure of 5 mmHg
139
Figure 4.18 Effect of feed temperature on the (a) permeation flux, (b)
permeate concentration and separation factor and (c) permeance and selectivity in the pervaporation dehydration of ternary azeotropic mixture of ethyl acetate/ethanol/water at a downstream pressure of 5 mmHg
145
Figure 4.19 Arrhenius plot of semi-logarithmic of (a) permeation flux and
(b) permeance against the reciprocal of absolute temperature 148
Figure 4.20 Effect of downstream pressure on the (a) permeation flux, (b)
permeate concentration and separation factor and (c) permeance and selectivity in the pervaporation dehydration of ternary azeotropic mixture of ethyl acetate/ethanol/water at 30°C
150
Figure 4.21 Pervaporation performances of BP-SILM-70 in dehydration of
ternary azeotropic mixture of ethyl acetate/ethanol/water for 120 hours operation time at 30°C and a downstream pressure of 5 mmHg
153
Figure 4.22 Parity plot of the predicted and experimental value for the
sorption concentration of water and ethylene glycol in BP-SILM-70
158
Figure 4.23 Exponential plot of the (a) diffusion coefficient of water versus
feed concentration of water and (b) diffusion coefficient of ethylene glycol versus feed concentration of ethylene glycol
160
xiv
Figure 4.24 Parity plot of the predicted and experimental value for the diffusion coefficient of (a) water and (b) ethylene glycol at different feed concentration
163
Figure 4.25 Comparison of the predicted and experimental pervaporation
performance in terms of (a) total permeation flux, (b) permeation flux of water and ethylene glycol, (c) permeance of water and ethylene glycol, (d) separation factor and (e) selectivity as a function of feed concentration
165
Figure 4.26 Arrhenius plot of semi-logarithmic of diffusion coefficient of
water and ethylene glycol against the reciprocal of absolute temperature
170
Figure 4.27 Parity plot of the predicted and experimental value for the
diffusion coefficient of (a) water and (b) ethylene glycol at different feed temperature
172
Figure 4.28 Comparison of the predicted and experimental pervaporation
performance in terms of (a) total permeation flux, (b) permeation flux of water and ethylene glycol, (c) permeance of water and ethylene glycol, (d) separation factor and (e) selectivity as a function of feed temperature
175
Figure 4.29 Exponential plot of the (a) diffusion coefficient of water and
(b) diffusion coefficient of ethylene glycol versus downstream pressure
180
Figure 4.30 Parity plot of the predicted and experimental value for the
diffusion coefficient of (a) water and (b) ethylene glycol at different downstream pressure.
182
Figure 4.31 Comparison of the predicted and experimental pervaporation
performance in terms of (a) total permeation flux, (b) permeation flux of water and ethylene glycol, (c) permeance of water and ethylene glycol, (d) separation factor and (e) selectivity as a function of downstream pressure
184
xv
LIST OF ABBREVIATIONS
[(C3H7)4N][B(CN)4] Tetrapropylammonium tetracyanoborate
[BF4]- Tetrafluoroborate ion
[Bmim] 1-butyl-3-methylimidazolium
[Bmim][BF4] 1-butyl-3-methylimidazolium tetrafluoroborate
[Cl]- Chloride ion
[NO3] - Nitrate ion
[NTf2-] Bis(trifluoromethyl-sulfonyl)imide ion
[Omim] 1-octyl-3-methylimidazolium
[PF6]- Hexafluorophosphate ion
ABE Acetone-butanol-ethanol
BLM Bulk liquid membrane
BP Buckypaper
BP-SILM Buckypaper supported ionic liquid membrane
CNTs Carbon nanotubes
CVD Chemical vapour deposition
EDX Energy dispersive X-ray
ELM Emulsion liquid membrane
GC Gas chromatograph
GPU Gas permeation unit
MMM Mixed-matrix membrane
MWCNTs Multi-walled carbon nanotubes
PDMS Polydimethylsiloxane
POMS Poly(octylmethylsiloxane)
PVA Polyvinyl alcohol
PVDF Polyvinylidene fluoride
PVP Poly(vinyl pyrrolidone)
SEM Scanning electron microscopy
SILM Supported ionic liquid membrane
SLM Supported liquid membrane
SWCNTs Single-walled carbon Nanotubes
xvi
TCE Trichloroethylene
TGA Thermogravimetric analysis
TOA Trioctylamine
UV-Vis Ultraviolet visible
xvii
LIST OF SYMBOLS
A Effective membrane surface area ai Thermodynamic activity of component i
𝑎𝑗𝑘 Interaction parameters of group j and k
c Concentration of component D Diffusion coefficient Dij Coupled diffusion coefficient
𝐷𝑖𝑀 Average diffusion coefficient of component i in the the membrane
𝐷𝑖0 Infinite diffusion coefficient of component i
𝐷𝑖0 Relative diffusion of component i
𝐷�𝑗𝑖 Effective diffusion coefficient
𝐸𝐷 Activation energy of diffusion
F Reagent factor for Karl Fischer titrator
J Permeation flux
𝑗 Molar flux
K Partition/solubility coefficient l Distance of diffusion
𝑚𝐵𝑃 Weight of BP
𝑚𝐵𝑃−𝑆𝐼𝐿𝑀 Weight of BP-SILM
𝑚𝐵𝑃−𝑆𝐼𝐿𝑀′ Weight of swollen BP-SILM
𝑃𝑖𝐺 Permeability of component i
𝑝𝑖𝐹 Partial pressure of component i in the feed
𝑝𝑖𝑃 Partial pressure of component i in the permeate
𝑝sat Saturated vapour pressure of component Q Quantity of the permeate collected 𝑄𝑘 Surface parameter of group k
𝑅𝑘 Volume parameter of group k r Relative volume parameter T Absolute temperature
∆𝑡 Time interval of pervaporation process V Partial molar volume of component
xviii
Vm Volume fraction of the membrane v Local velocity of component
𝑣𝑘(𝑖) Number of group k in component i.
W Weight of the permeate sample in titration flask
𝑤𝑖′ Weight fraction of component in the membrane
X Weight fraction of component in the feed
𝜒𝑖𝑚 Binary interaction parameter between component i and membrane
X’j Fraction of group j in the liquid x Mole fraction of component
Y Weight fraction of component in the permeate α Membrane selectivity
β Separation factor
βDiff Diffusion selectivity
βSorp Sorption selectivity
𝛾𝑖 Activity coefficient of component i
𝛾𝑖𝑅 Residual activity coefficient of component i
𝛾𝑖𝑐 Combinatorial activity coefficient of component i
𝛿 Membrane thickness
𝜀 Plasticization coefficient
∅ Volume fraction of component
𝛤𝑘 Activity coefficient of group k
𝛤𝑘𝑖 Activity coefficient of group k in pure component i.
𝜃𝑖 Surface fraction of component i
�̅�𝑀 Average density of the membrane
xix
SINTESIS MEMBRAN CECAIR IONIK BERPENYOKONG KERTAS-
BUCKY UNTUK PROSES PENYEJATTELAPAN
ABSTRAK
Membran cecair berpenyokong adalah salah satu konfigurasi membran cecair
yang menggunakan bahan fasa cecair sebagai membran dan diperangkap ke dalam
substrat berliang. Sejak kebelakangan ini, idea tentang penggunaan membran cecair
berpenyokong dalam proses penyejattelapan telah menarik tumpuan ramai penyelidik.
Tetapi penggunaan membran cecair berpenyokong menghadapi masalah
ketidakstabilan yang berpunca daripada kehilangan membran cecair. Kajian ini
bertujuan untuk membangunkan membran cecair berpenyokong dengan kestabilan
yang tinggi dengan menggunakan kertas-bucky sebagai substrat berliang dan
diperangkap dengan cecair ionik 1-butil-metilimidazolium tetrafluoroborat
[Bmim][BF4] untuk membentuk membran cecair ionik berpenyokong kertas-bucky.
Kertas-bucky terdiri daripada kelompok nano-tiub karbon dinding berlapis mampu
memerangkap membran cecair ionik secara berkesan disebabkan oleh saiz liang yang
kecil and struktur liang yang berliku-liku. Untuk meningkatkan lagi kestabilan
membran, [Bmim][BF4] telah dicampur dengan polivinil alkohol sebelum
diperangkap dalam kertas-bucky. Struktur membran cecair ionik berpenyokong
kertas-bucky yang terhasil didapati berbeza dengan membran asimetrik, di mana fasa
membran dan sokongan telah digabungkan dalam satu lapisan. Struktur tersebut
membolehkan pembentukan membran simetri yang tipis tanpa menjejaskan sifat
mekanikal membran. Prestasi membran cecair ionik berpenyokong kertas-bucky
dalam proses penyejattelapan yang melibatkan campuran perduaan yang terdiri
xx
daripada etilena glikol dan air menunjukkan keupayaan membran tersebut dalam
penyahhidratan larutan akueus etilena glikol. Kewujudan kertas-bucky dan
[Bmim][BF4] didapati telah meningkatkan prestasi pemisahan dan kebolehtelapan
intrinsik membran. Membran cecair ionik berpenyokong kertas-bucky telah
menunjukkan prestasi penyejattelapan yang tinggi dengan fluks penelapan yang
bernilai 102 g∙m-2∙j-1, faktor pemisahan setinggi 1014, kebolehtelapan air yang
bernilai 13106 GPU dan kememilihan membran untuk air yang bernilai 13 dengan
berat air dalam kepekatan larutan suapan sebanyak 10% pada suhu 30 °C dan 5
mmHg tekanan hiliran. Di samping itu, membran cecair ionik berpenyokong kertas-
bucky juga mampu untuk memisahkan campuran pertigaan; etil asetat, etanol dan air
yang membentuk azeotrop. Fluks penelapan sebanyak 385 g∙m-2∙j-1, faktor pemisahan
yang bernilai 247, kebolehtelapan air 4730 GPU dan kememilihan membran untuk
air yang bernilai 39 telah diperolehi pada suhu 30 °C dan 5 mmHg tekanan hiliran.
Membran cecair ionik berpenyokong kertas-bucky telah mempamerkan prestasi yang
tekal dalam operasi selama 120 jam. Pekali resapan etilena glikol dan air pada
operasi parameter yang berlainan telah dianggar dengan menggunakan model
matematik semi-empirikal berdasarkan pengubahsuaian persamaan Maxwell-Stefan.
Dengan merujuk pada pekali resapan yang dianggar, pemisahan membran cecair
ionik berpenyokong kertas-bucky dalam proses penyejahttelapan bagi
penyahhidratan campuran perduaan etilena glikol/air adalah dikawal oleh proses
resapan.
xxi
SYNTHESIS OF BUCKYPAPER SUPPORTED IONIC LIQUID MEMBRANE
FOR PERVAPORATION PROCESS
ABSTRACT
Supported liquid membrane (SLM) is one of the liquid membrane
configurations that employ a liquid phase substances as membrane and immobilized
in a porous supporting membrane. Recently, the idea of using SLM in pervaporation
process has attracted a great deal of research attention. However the use of SLM in
pervaporation has always suffered from instability problem which is mainly due to
the displacement of liquid membrane. In the present research work, it is aimed to
develop a high stability SLM by employing buckypaper (BP) as supporting
membrane and immobilized with an ionic liquid 1-butyl-3-methylimidazolium
tetrafluoroborate [Bmim][BF4] to form a buckypaper supported ionic liquid
membrane (BP-SILM). The BP, which is composed of entangled assemblies of multi-
walled carbon nanotubes (CNTs), can effectively entrap the infiltrated the ionic
liquid membrane due to its smaller pore size and highly tortuous porous structure. In
order to further enhance the membrane stability, the [Bmim][BF4] was blended with
polyvinyl alcohol (PVA) prior to the immobilization in the BP. The resulted BP-
SILM structure, in which the membrane and support phase were merged into a single
layer, was found to be different from that of conventional asymmetric membranes.
The BP-SILM structure allows the formation of a thinner symmetric membrane
without compromising its mechanical properties. The pervaporation performances of
the BP-SILM in the binary mixture of ethylene glycol and water showed an excellent
capability to dehydrate ethylene glycol aqueous solutions. The presence of BP and
xxii
[Bmim][BF4] was observed to significantly enhance the separation performance and
the intrinsic membrane permeability. The BP-SILM exhibited high pervaporation
performance with a permeation flux of 102 g∙m -2∙h-1, separation factor as high as
1014, water permeance of 13106 GPU and membrane selectivity of 13 for water with
10 wt.% feed concentration of water at 30 °C and 5 mmHg downstream pressure. On
the other hand, the BP-SILM was also capable to break ternary azeotropic mixtures
of ethyl acetate, ethanol and water. A permeation flux of 385 g∙m -2∙h-1, separation
factor of 247, water permeance of 4730 GPU and membrane selectivity of 39 for
water were obtained at 30 °C and 5 mmHg downstream pressure. The BP-SILM also
demonstrated a robust pervaporation performance over an operation of 120 hours.
The diffusion coefficients of ethylene glycol and water at different operating
parameter were estimated using a semi-empirical mathematical model based on
modified Maxwell-Stefan equation. Based on the estimated diffusion coefficient
obtained, the separation of BP-SILM in pervaporation dehydration of ethylene
glycol/water binary mixture is more on diffusion control.
1
CHAPTER 1
INTRODUCTION
1.1. Pervaporation
For the past few decades, pervaporation has been viewed as an effective
strategy for liquid separation. The term “pervaporation” was first introduced by
Kober (1917) when reporting the selective permeation of water from aqueous
solutions of albumin and toluene through a cellulose nitrate film. In general, a
pervaporation system is composed of a dense membrane that serves as a separating
barrier between two compartments and regulates the mass transport across the
membrane. The driving force for the separation in pervaporation process is mediated
by chemical activities difference created between the upstream and downstream sides
of a membrane, for this reason, a vacuum pump or sweeping gas is usually applied at
the downstream side. The component which is preferentially removed from the liquid
mixture possesses higher affinity to permeate through the membrane and undergoes a
phase change from liquid to vapour. The overview of the molecule transport in
pervaporation process is illustrated in Figure 1.1.
Recommended